1. Field of the Invention
The present invention relates to an apparatus for manufacturing polyarylene sulfide and a process for manufacturing polyarylene sulfide using the apparatus. More particularly, the present invention relates to a corrosion resistant apparatus for manufacturing polyarylene sulfide which is used suitably in electricity-electronic fields, the vehicle field such as automobiles, and the heat resistance material field, and to an efficient and inexpensive process for manufacturing polyarylene sulfide using the apparatus.
2. Description of the Background Art
In the manufacture of polyarylene sulfide by the reaction of, for example, an alkali metal sulfide and a dihalogenated aromatic compound in a non-proton organic solvent, a material which is expensive and difficult to work, such as titanium, has been used for the reaction equipment. Because of this, increased plant construction cost and increased fixed costs have been unavoidable.
To expand the demand of the polyarylene sulfide as an engineering plastic, a reduction in its manufacturing costs has been strongly desired.
Specifically, high corrosion resistant characteristics are demanded of various apparatuses for manufacturing polyarylene sulfide, such as dehydration vessels, polymerization vessels, purification tanks, distillation towers, transportation pipes, storage tanks, separation tanks, and solvent removal tanks, because these apparatuses are exposed to strong alkali components, sulfides, chlorides, organic solvents, and the like at a high temperature of 200.degree. C. or higher during the polymerization of polyarylene sulfide. Even stainless steel which is said to be strongly resistant to corrosion produces metal sulfides, such as iron sulfide or nickel sulfide, by a reaction with a sulfide which is present in the polymerization process. Almost all these metal sulfides are ultimately included in the produced polyarylene sulfide. For this reason, titanium materials which excel in corrosion resistance have conventionally been used.
For example, Japanese Patent Publication No. 39537/1991 describes the use of a titanium material for a liquid-contact section of the dehydration step.
An apparatus for the manufacture of polyarylene sulfide made of iron-chromium ferrite type stainless steel having a specific composition is described in Japanese Patent Publication No. 213338/1989.
Japanese Patent Publication No. 49761/1994 describes a method for suppressing corrosion in the reaction vessel by reacting a mixture of an alkali metal sulfide, water, and a non-proton organic polar solvent at a ratio of 1:10-20:1-10 with heating to obtain a dehydration reaction mixture and reacting this reaction mixture reaction with a dihalogenated aromatic compound.
The titanium material disclosed in Japanese Patent Publication No. 39537/1991, however, is more expensive and its workability is poorer than stainless steel and the like, requiring stringent control during manufacture of the apparatus, resulting in increased manufacturing costs.
Although the apparatus described in Japanese Patent Publication No. 213338/1989 appears to be fairly close to a commercial level with regard to corrosion resistance, this apparatus is not necessarily satisfactory. In addition, it is difficult to judge the applicability in practical use of the apparatus from the data disclosed, because the corrosion data used for calculating the yearly corrosion quantity is based on an immersion test carried out for only a very short period of time in comparison with an industrial production period.
Moreover, because the polyarylene sulfide produced by the method disclosed in Japanese Patent Publication No. 49761/1994 contains several ppm of iron, this polyarylene sulfide is unsuitable for use in applications to electronic components and films requiring a high level of surface smoothness.
In addition, stainless steel is known to produce cracks due to stress corrosion when used for a long time under conditions such as those required for the polymerization of polyarylene sulfide.
The present invention has been completed with an object of solving these problems and providing an apparatus for the manufacture of polyarylene sulfide with excellent corrosion resistance and an efficient and inexpensive process for manufacturing the polyarylene sulfide using this apparatus.
In order to achieve the above-mentioned object, the inventors of the present invention have conducted extensive studies on various materials which make up the apparatuses. As a result, the inventors have found that an apparatus for the manufacture of polyarylene sulfide which exhibits almost the same corrosion resistance as the titanium material can be manufactured from at least one material selected from the group consisting of Incoloy-type alloys, Carpenter-type alloys, Hastelloy-type alloys, and two phase stainless steel. This finding has led to the completion of the present invention.